Dishwasher comprising a sensor unit for determining a rotation movement of a spray arm

ABSTRACT

The invention proposes a dishwasher comprising a working chamber, comprising at least one spray arm which is arranged in a rotatable manner in the working chamber, and comprising a metering apparatus for supplying and metering a substance, such as detergent, rinse aid etc., into the working chamber, which metering apparatus is designed as an insert part comprising a housing for insertion into a recess in an inner wall of the working chamber, for example in the door of the working chamber, and comprising a sensor unit for identifying a spray arm movement in the working chamber of the dishwasher, which sensor unit is arranged at least partially in a housing of the metering apparatus, wherein the sensor unit  11  comprises at least one infrared transmitter  12  and/or one infrared receiver  13.

The invention relates to a dishwasher comprising a working chamber and asensor according to the preamble of claim 1.

A dishwasher of this kind is described, for example, in DE 10034546 A1.In the case of this item according to the prior art, the interior of adishwasher is monitored by means of one or more radar sensors using theDoppler effect. This sensor system is very complicated and accordinglycostly. Furthermore, it has not been possible to realize technicallyproblem-free functioning of a dishwasher of this kind to date.

The object of the invention is to propose a dishwasher having improvedprogram control, proceeding from a dishwasher according to the preambleof claim 1.

This object is achieved by the characterizing features of claim 1.

Accordingly, a dishwasher according to the invention comprising a sensorunit for identifying a spray arm movement in the working chamber isdistinguished in that said sensor unit comprises at least one infraredtransmitter and/or one infrared receiver.

This sensor unit is at least partially in the housing of the apparatuswhich is designed as an insert part and serves to supply and meter aworking substance, such as a detergent, rinse aid etc.

An apparatus of this kind is called a metering apparatus in the textwhich follows. Furthermore, the terms “warewasher”, “dishwashingmachine” and “dishwasher” are used synonymously in the text whichfollows, as are the terms “jet of water” and “jet of washing solution”.

A sensor unit according to the invention can be used to check programsequences during operation. In particular, it is therefore possible todetect whether the spray arm and/or which spray arm is rotating properlyor is malfunctioning.

The use of infrared light allows reliable detection, in particular ofthe movement of the spray arm, largely without problems under theenvironmental conditions in the working chamber of a dishwashing machineduring operation. Spray arms which are at a relatively large distancefrom the sensor unit or in an unfavorable position, for example inrespect of the angular orientation, can also be detected owing to thelarge range of an infrared beam.

In this case, the functional principle of the sensor unit is based oninfrared light being emitted by an infrared transmitter, being reflectedin the working chamber and being detected again by an infrared receiver.

In order to identify spray arm rotation, an infrared beam, for example,can be reflected to the receiver by means of a reflector which islocated in a stationary manner in the working chamber of the machine,wherein changes in the IR beam, for example in the intensity, which areinduced by a rotating spray arm, a component which is fastened to thespray arm or by a jet of water or washing solution from the spray armcan be detected.

In this case, the stationary reflector used can be a separate componentor a component which is present in any case, for example a region of thewall of the working chamber.

In another embodiment of the invention, a beam which is emitted by theIR transmitter is reflected into the receiver by the rotating spray armor an element which is connected to said spray arm, for example a regionof the spray arm wall, a separate reflector element which is fastened tothe spray arm, a jet of water or washing solution from a spray armnozzle etc. These reflections are therefore directly correlated with therotation of the spray arm.

The reflections and/or changes in reflections are to be detected in asignificant manner in particular when they take place in the vicinity ofthe transmitter and/or receiver, for example by a spray arm or jet ofwater rotating directly past the transmitter/and or receiver.

In a particular embodiment of the invention, reliably detectablereflection of the infrared light is ensured in that at least one sprayarm nozzle is oriented in such a way that the jet of water or the jet ofwashing solution at least partially crosses the beam path of theinfrared light. The reflections desired according to the invention canbe created by the water or the washing solution in this case.

In an embodiment of this kind, the beam path of the infrared light ispreferably formed, for example by additional optical elements, such thata focal point or at least one focusing zone is produced which is struckby said jet of water or washing solution.

In another likewise advantageous embodiment of the invention, thedesired reflection is created by the spray arm itself. To this end, thearrangement and surface design of the spray arm can be provided in acorresponding manner. For example, a spray arm can have, at least inregions, a coating which is highly reflective to infrared light.Furthermore, the beam path of the infrared light and the position of thespray arm relative to one another can be arranged in such a way that thespray arm crosses the beam path at least by way of its reflection zone.A beam path which has a focal point or at least one focusing zonethrough which the spray arm is passed by way of its reflection zone canadvantageously also be used in this embodiment.

In a further advantageous embodiment of the invention, the spray arm isequipped with a special reflector for infrared light. Reflectors of thiskind can be formed by mirror surfaces and/or by refraction of light,possibly with the additional use of optical elements, so that incidentinfrared light is reflected in a targeted manner. In the visible range,reflectors of this kind are also known by the term “cat's eye” or“Luneburg lens”.

With reflectors of this kind, a reflection angle can also be provided inparticular, which reflection angle takes into account the relativearrangement of the infrared receiver in relation to the infraredtransmitter.

The housing of the metering apparatus, which housing contains the sensorunit, is advantageously of water-tight design. In this case,accommodating the sensor unit in the housing of the metering apparatuswhich is present in any case makes it easier to arrange it in theinterior of the working chamber of the warewasher. Firstly, it is notnecessary to provide an additional opening in the inner wall or the doorof the working chamber as a result of this since the metering apparatusis to be arranged in a recess of this kind in the inner wall in anycase. Furthermore, the housing is already of water- and washingsolution-tight design in the case of the known metering apparatuses. Allof the electrical control elements, even for the metering apparatus,which are located in the interior of the dishwashing machine door arealready protected against the water or the dishwashing solution by thedesign of the housing according to the prior art.

Therefore, a sensor unit can advantageously be accommodated within ametering apparatus of this kind without relatively major sealingproblems, for which reason an infrared-permeable window, for example, isprovided in the housing. A window of this kind can be realized in asimple manner by appropriate seals or else by a fixed connection, forexample by welding or adhesive bonding, to the housing wall of themetering apparatus in a reliably sealed-off manner.

In an advantageous embodiment of the invention, the additionalarrangement of guide elements is further provided in order to keep waterwhich is running off away from the beam path of the infrared light afterpassing through the spray arm. Water which is running down could causereflections which produce undesired interference signals. Owing to guideelements, for example in the form of a canopy above the outlet of theinfrared light from the housing, for example above a passage window, itis possible to ensure that water which is running down is guidedlaterally around said outlet.

In another embodiment of the invention, guide elements of this kind areprovided on the inner wall of the working chamber, as a result of whichthe entire that here apparatus is protected against water which isrunning down, as is the infrared beam path.

Furthermore, the sensor unit, in particular the infrared transmitterand/or receiver, is preferably arranged in such a way that it is notsituated directly in a jet of water or washing solution from a spray armnozzle. Interference signals due to undesired reflections are alsoavoided as a result.

In a particular embodiment of the invention, the time sequence of thesensor signal is detected and an evaluation unit is provided in order todetect the periodicity or frequency of the sensor signal which isinduced by the rotating spray arm.

Since the rotational movement of the spray arm is to be monitoredaccording to the invention, it can be assumed that the signal is aperiodic or frequency-dependent signal. Therefore, owing to the timedetection of the sensor signals with subsequent evaluation in anelectronic evaluation unit, selective evaluation for periodic signalscan therefore be performed. On account of this measure, virtually allnon-periodically occurring interference signals are already filtered orsuppressed.

By virtue of determining the frequency, the rotation speed or speed ofthe spray arm can then be determined. if no periodic signal can bedetected, this is a sign of a stationary spray arm, but at least of anon-freely rotating spray arm.

In the event of a malfunction of this kind of the spray arm, this canbe, for example, displayed to an operator or else an intervention in thecontrol of the program sequence can be made.

In a particular embodiment of the invention, an analog evaluationcircuit is provided in order to detect the periodicity or frequency ofthe sensor signal which is induced by the rotating spray arm. A circuitof this kind can be realized, for example, using a so-called PPL (phaselock loop). Therefore, an oscillating input signal can be compared withthe sensor signal in a comparator or differential amplifier and changesin the output voltage can be used to draw conclusions about properrotation of a spray arm. Even if digital components are technicallyreadily available for evaluating a sensor signal according to theinvention, the use of an analog circuit may provide the technically moreadvantageous solution from cost points of view given appropriatenumbers. The combination of an analog circuit with a digital evaluationarrangement, which intervenes only given a faulty output voltage of theanalog circuit for example, would also be conceivable.

In the case of a digital evaluation unit, different algorithms canfurther be provided in order to analyze and to rule out disturbinginfluences. Instead of or in combination with the use of the periodicityas stated above, integration of the signal peaks, that is to saydetermining the area covered by the signal, for example, can also beused to identify and to rule out fault peaks. In this way, fault signalswhich do not follow the time sequence and the intensity of thereflections generated by the spray arm or the jet of water or washingsolution can be identified and ruled out. Threshold value analysis canalso be used instead of or in addition to other fault identificationmethods.

An exemplary embodiment of the invention is illustrated in the drawingand will be explained in more detail below with reference to thefigures.

Specifically:

FIG. 1 shows a schematic cross section through a warewasher comprising aspray arm,

FIG. 2 shows a plan view of the inside of the door of a 8 warewasher,

FIG. 3 is an illustration of a metering apparatus, and

FIG. 4 shows an example of a sensor signal which can be measured bymeans of an infrared transmitter and/or infrared receiver.

FIG. 1 schematically illustrates the warewasher 1 comprising adishwashing chamber 2 in section. With dish racks 3, 4 are located inthe dishwashing chamber 2, a spray arm 5, 6 being arranged in arotatable manner beneath each of said dish racks.

A warewasher door 7 is fitted to the front side in a rotatable manner,as is indicated by a rotation axis 8. A metering apparatus 9 for addingdishwashing agent is located in the warewasher door 7.

A sump container 10 is located in the base of the warewasher 1, saidsump container containing, for example, the customary filters and thewater outlet.

FIG. 2 shows the arrangement of an infrared sensor unit 11 in themetering apparatus 9, which infrared sensor unit comprises an infraredtransmitter 12 and an infrared receiver 13. The metering apparatus 9 isinserted into the warewasher door 7, as already described with referenceto FIG. 1. The metering apparatus 9 comprises, in a customary manner, aflap 14 for closing a dishwashing agent chamber, an outflow opening 15for metering rinse aid, and an inspection window 16 and a refillingopening 17 for the rinse aid.

The evaluation and control unit can also be arranged in the interior ofthe warewasher door, as indicated in FIG. 1. At the location of theevaluation and control unit 18 indicated in FIG. 1, said evaluation andcontrol unit can be connected directly to the displays, buttons andother operator control elements required to operate the machine.

FIG. 3 illustrates a metering apparatus for installation into awarewasher door according to the invention, wherein a storage means 1for receiving detergent is provided. This detergent is supplied to thecleaning chamber for the dishes in a controlled manner during thecleaning phase of the dishwasher. In the process, a cover 2 is opened,so that the detergent can run out or be washed out of the storage means1. A roof-like projection 20 serves as a guide element in order todeflect water or washing solution which is running down.

The infrared sensor unit 11 is installed, for example, at the edge ofthe housing 19 of the metering apparatus

FIG. 4 illustrates, by way of example, a time sequence of an infraredsensor signal. The horizontal axis of the graph shows the time t, whilethe vertical axis illustrates the intensity I. The sensor signal Sexhibits different peaks P1 to P5 which are each arranged periodicallyas a function of time. The respective time points t1 to t5 are marked bycorresponding arrows.

The graph according to FIG. 4 shows, by way of example, two furtherpeaks S1 and S2 which constitute interference signals which can becaused, for example, by undesired reflections at dripping water or thelike.

These interference peaks S1 and S2 can be identified and eliminated bysuitable evaluation by means of the evaluation unit 18. This evaluationcan be configured, for example, in such a way that only periodicallyrecurring signals P1 to P5 are perceived as real sensor signals,non-periodic signals however being perceived as interference signals.Another way of identifying the interference signals involves, forexample, integrating the corresponding signal peaks with respect totime, as a result of which the area which is covered by the peaks ismathematically determined. Since an integral value is to be expectedwithin a specific interval given regular sensor signals, other signals,such as the linear interference signals S1 and S2 for example, can beidentified and ruled out in this way.

These exemplary methods of else further methods for identifyinginterference signals, for example by means of threshold values inrespect of the intensity or the like, can be used on their own or elsein combination with one another.

If a malfunction, for example a stationary spray arm or a spray armwhich is rotating too slowly, is identified on the basis of the sensorsignal, thio can be displayed to the operator in a display.

The warewasher according to the invention can also be controlleddepending on the sensor signal. For example, the quantity of waterand/or the pump pressure can be varied. Nozzles which are controllablein respect of the orientation of the jet and/or shape of the jet arealso optionally conceivable.

LIST OF REFERENCE SYMBOLS

-   1 Warewasher-   2 Dishwashing chamber-   3 Dish rack-   4 Dish rack-   5 Spray arm-   6 Spray arm-   7 Warewasher door-   8 Rotation axis-   9 Metering apparatus-   10 Sump container-   11 Infrared sensor unit-   12 Infrared transmitter-   13 Infrared receiver-   14 Flap-   15 Outflow opening-   16 Inspection window-   17 Refilling opening-   18 Evaluation and control unit-   19 Housing-   20 Roof-like projection-   T Time-   I Intensity-   P1 Peak-   P2 Peak-   P3 Peak-   P4 Peak-   P5 Peak-   T1 Time point-   T2 Time point-   T3 Time point-   T4 Time point-   T5 Time point-   S1 Interference peak-   S2 Interference peak

1. A dishwasher comprising a working chamber, comprising at least onespray arm which is arranged in a rotatable manner in the workingchamber, and comprising a metering apparatus for supplying and meteringa substance, such as detergent, rinse aid etc., into the workingchamber, which metering apparatus is designed as an insert partcomprising a housing for insertion into a recess in an inner wall of theworking chamber, for example in the door of the working chamber, andcomprising a sensor unit for identifying a spray arm movement in theworking chamber of the dishwasher, which sensor unit is arranged atleast partially in a housing of the metering apparatus, characterized inthat the sensor unit 11 comprises at least one infrared transmitter 12and/or one infrared receiver
 13. 2. The dishwasher according to claim 1,characterized in that the spray arm 5, 6 and/or a jet of water orwashing solution from a spray nozzle crosses the beam path of theinfrared transmitter 12 and/or infrared receiver 13 during the rotationof the spray arm.
 3. The dishwasher according to claim 1 wherein thespray arm 5, 6 comprises a reflector for infrared light.
 4. Thedishwasher according to claim 1 wherein the housing 19 of the meteringapparatus 9 is of water-tight design.
 5. The dishwasher according toclaim 3 wherein the housing 19 of the metering apparatus 9 has guideelements 20 in order to keep the beam path of the infrared light atleast partially free of water running off from the housing.
 6. Thedishwasher according to claim 5 wherein the guide elements are designedas a roof 20 over an infrared-permeable passage in the housing 19 of themetering apparatus
 9. 7. The dishwasher according to claim 1 wherein theinner wall of the working chamber has guide elements in order to keepwater which is running off away from the beam path of the infraredlight.
 8. The dishwasher according to claim 1 wherein the sensor unit 11is arranged such that it is not situated directly in a jet of water froma spray arm nozzle.
 9. The dishwasher according to claim 3 wherein atime sequence of the sensor signal is detected and an evaluation unit isprovided in order to detect the periodicity or frequency of the sensorsignal which is induced by the rotating spray arm.
 10. The dishwasheraccording to claim 1 further comprising an analog evaluation circuit.11. A metering apparatus for supplying and metering a substance, such asdetergent, rinse aid etc., into the working chamber of a dishwasheraccording to one of the preceding claims, which metering apparatus isdesigned as an insert part comprising a housing for insertion into arecess in an inner wall of the working chamber, for example in the doorof the working chamber, and comprises a sensor unit for identifying aspray arm movement in the working chamber of the dishwasher, whichsensor unit is arranged at least partially in the housing, characterizedin that the sensor unit comprises at least one infrared transmitterand/or one infrared receiver.